The invention relates generally to subscriber line interface circuits and more specifically to a method and an arrangement for shortening the recovery time of a line driver in a subscriber line interface circuit after an overvoltage on its output terminal.
In subscriber line interface circuits (SLICs), line drivers connected to tip and ring wires of respective transmission lines, have to be turned off when the voltage on the tip or ring wire comes close to the negative supply voltage of the line drivers.
The line drivers are turned off in order to avoid an uncontrolled function that could lead to the destruction of the line drivers.
When turned off, the line drivers are put in a high-impedance state with no ability to sink or source current. This may lead to that the line drivers are stuck in this state for a longer or shorter time.
An example of a situation when this can occur is when a charged line is connected to the SLIC after a ringing sequence.
The object of the invention is to eliminate these problems with the known line drivers.
This is obtained by the method and the arrangement in accordance with the invention by initiating a current generation before the turn-off function is activated with the purpose of xe2x80x9cpullingxe2x80x9d the tip and/or ring wires, i.e. actually the voltage of the tip and/or the ring wires, into the active operating range of the line drivers.
Hereby, the recovery time of the line drivers after an overvoltage will be considerably shortened.